Sani francisco bridge co



May 6, 1924. 1,492,985; w. F. HUNTER v SPIRAL TUNNEL ENTRANCE Filed June 9, 1923 Patented May 6, 1924.

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sari Francisco BRIDGE 00., or s ift,

j TUNNEL,

Application fil'e'd June 9,3923; Serial my. "044,472.-

To all whom it may concern:

Be it known that 1, WILLIAM F. HUNTER, a citizen of the United States, residing at Oakland, in the county of Alameda and State of California, have invented a new and useful Spiral Tunnel Entrance, of which the following is a specification.

This invention relates to subway, tunnel and tube structures, and more particularly to a novel form of approach employed at the ends. The primary object of the invention is to provide an approach that will eliminate the necessity of occupying or acquiring valuable property for straightaway approaches, and thereby reducing the. cost of subway and tube construction to a minimum.

Anotherobject of the invention is to decrease the distance to be travelled in passing through the subway, as, on account "of the smaller diameter of circle and steeper grade for the descending traific, as compared with that of the larger diameter of circle and easier grade for ascending traflic, makes a substantial saving in the total distance to be traversed.

A still further object of the invention is to provide approach structures which may be constructed at a location remote from the subway, and readily floated and sunk into position, as this would, in'many cases,

efiect a substantial saving in cost of con-- struction. Where the conditions are advantageous, the excavation may be made and the approach structures constructed directly in position.

This form of approach structure may be used in connection with two tubes, one for traffic in each direction, or it may be usedin connection with a single tube carrying trafiic in both directions.

With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed, may be made within the scope of what is claimed, without departing from the spirit of the invention.

Referring to the drawings: Figure 1 15 an elevational view disclosmg approaches constructed 1n accordance with the invention, as supplied at the ends" of a subway construction.

Flgure 2 is a vertical sectional view through an approach constructed in accordance with the invention.

Figure 3 is a diagrammatical view of the same being circular or polygonal in formation, as clearly shown by Figure 3 of the drawings. 7

The reference character 6 designates a spirally-arranged roadway supported by the posts 7 and 8', the posts 8 providing a dividing line dividing the roadway of the approach, into lateral trafiic ways permitting uninterrupted trafiic in opposite directions. A tower is indicated at 9 and is disposed substantially centrally of the approach, the tower being provided with openings 10 at the upper end and pipes 10 at the lower end to ventilate the subway.

y A winding stairway designed at 11 encircles the tower 9, whereby pedestrians may use the approach to facilitate trafiic. An elevator or series of elevators for pedestrians may also be installed in the tower or at other convenient location.

As shown, the subway, which may be of any desired construction, is indicated at 12, and may embody either a pair of tubes or a single tube which connects with a spirallyarranged road surface through the openings 13.

In the use of'the device, it is to be understood that an approach as shown and described, is to be employed at opposite ends of a subway, thereby reducing the grade ordinary necessary in ascending from a subway to the minimum, and at the same time reducing the ground surface required for the usual long approaches to the minimum.

It is contemplated in construction of the approach structures of this character'either to construct them in their permanent 'position after excavating the ground, or to construct them at points remote and to convey them to their proper places and sink them, as for example, at the edges of rivers or bodies of water, wherein subways are to be built thereunder.

What I ciaim is p An approach for subways including a circular metallic body portion adapted to be sunk in a body of water, the body portion being formed of water-proof material,

a spirally arranged road surface Within the In testimony that I claim the foregoing as 15 my own, I have hereto aflixed my signature 1n the presence of two witnesses.

WILLIAM F. HUNTER.

Vitnesses BENJ. BIRCH, M. K. BI LSoN. 

